This invention relates to a method and apparatus for connecting belt fasteners to conveyor belt ends by connectors such as rivets or staples. The invention is described hereinafter in connection with the attachment of hinged belt fasteners having an upper plate which is inclined upwardly to be spaced from the top surface of the belt prior to application thereto and a lower plate, the plates being attached to the belt by staples. However, the method and apparatus are also useable with plate fasteners which are separate plates which are not connected by a hinge portion and in which the top plate lays flat against the upper surface of the belt prior to application of the staples or rivets.
One manner of attaching belt fasteners to belt ends with staples is disclosed in U.S. Pat. Nos. 4,111,080 and 4,333,217. These patents disclose a staple guide block which is positioned over several fasteners for guiding an impact applying member that is manually driven by being hit by a mallet or hammer to drive the staples from the guide block into the holes of the upper plate and through the belt carcass into the holes in the underlying plate. There is an initial set or bending of the staple ends through about 45° by a first anvil. Then there is a second stage of the application procedure without the use of the guide block wherein the staples are hit directly by a hammer to do the final clinching or bending over of the ends of the staples by a second anvil to tightly engage the lower surface of the lower plate of the belt fasteners.
A particular problem with the use of these manually operated fastener systems, which do not use a motor drive to supply the force at least through the initial set of application, is that of fatigue of the operator. More specifically, if the operator has to do very wide belts or has to do a large number of belt splices, the swinging of the relatively heavy mallet or hammer to penetrate the belt to initially set the staple and/or a second swinging of the heavy mallet to do the final set of the staple ends may result in considerable operator fatigue.
Additionally, the speed of operation for a manual initial set and a final clinching set operation is limited such that there is a need for a faster system. Some prior systems have proposed power or motor driven tools rather than a manually swung mallet to force the staple ends through the belt for the initial setting of the staples ends. In one of these systems, the operator lightly taps the tops of a hinge type belt fastener to compress the upper plate against the top of the belt so as to be substantially in a horizontal plane with the upper, top surface of the belt. A fixture or staple guide is fitted on the tool base and is located relative to the belt fastener and is used to guide the staple which is power driven through the staple guide and the belt to cause the lower ends of the staples to be bent by an underlying anvil into an initial set. One staple at a time is driven and it is necessary to reposition the tool and gun for each staple location. Where two staples are used for each belt fastener, this will require a repositioning of the staple power motor driven gun of this system twice in order to drive both of these staples for this single fastener into the belt to accomplish the initial set operation. After all of the staples have been initially set, the staple guide is removed from the tool and a gauge pin is inserted into the fastener loops. The final or clinching of the staples can be either done manually with a hammer or by using a different, hydraulic tool. Thus, the above system fastens only a single staple at a time and uses a different tool to accomplish the final setting operation.
There are manual systems that use an impact applying member which drives multiple staples with the single impact applying member having multiple punches, but this system is laborious and slow (see the '080 patent and U.S. Pat. No. 4,688,711 for rivet connectors). Another similar prior system shown in U.S. Pat. No. 5,524,808 also has an impact applying member for rivet connectors. In this system, a power tool applies the drive force to the impact applying member. However, after actuation of the tool for a rivet driving operation, the tool and then the separate impact applying member have to be moved separately from each other to the next set of guide bores and associated rivets for the next rivet driving operation with this sequence of operations repeated until the belt splice is complete. As is apparent, the separate tool and impact applying member requires time and labor for removing the tool from the impact applying member, removing the punches or prongs of the impact applying member from the guide bores, placing the punches in the next set of guide bores and then aligning the tool back over the impact applying member before the tool is actuated.
In another prior system that is commercially available, a pneumatic gun or tool has a staple and staple magazine and a lower guide block attached to the lower end of the pneumatic gun. The lower guide block carries pins that fit into alignment holes for an anvil base to align the power driven drive rod against the staple. The staple may be driven once by the pneumatic drive tool to initially bend or set a single staple. After the operator performs the initial set driving of the staple ends, a final manual setting operation using a hammer accomplishes the clinching of the staple ends. In this system, only a single staple is driven so that staples are applied one at a time, and the staples sometimes jam in the gun and the drive rods are subject to breaking. The final manual staple setting operation requires set-up time and manual labor in generating the final set force slowing the process for completing the belt splicing operation.
In stapling of a belt fastener to a belt, the staple is driven into a cup-shaped recess in the fasteners upper plate which receives the head of the staple. The legs depending from the head of the staple are driven through a pair of holes separated by a thin piece bridge in the upper plate recess, and the bridge may be broken if too much force is applied to it. Also, the staple head may be damaged if too much force is applied to it. Excessive force from a power drive tool may also create a dent or dip in the front edge portion of the inner fastener plates. It is desirable to drive the staple without any denting, marring or marking of either the staple or the fastener itself. The likelihood of such damage is increased in applications in the field such as coal mines or construction sites where pneumatic pressure may be unregulated or fluctuates considerably, e.g., between 65 to 100 psi, and hence the force generated and applied to the staple and fastener may be larger than desired potentially causing damage to the staple or belt fastener, or both.
In some instances the guide block is attached to the power gun itself and in other instances the guide block is separate from the power gun. A lean or inclination of the gun relative to the staple may cause a misfire. This results because the staples are initially at an incline to the vertical and the upper plate is not horizontally disposed when the belt end is inserted between the fastening plates. Thereafter, if the gun is not properly aligned with the inclined staple, the upper part of the staple may be folded over such that the lower staple end legs do not penetrate the belt to pass through the holes in the bottom plate, which is termed a “misfire.” Another type of misfire occurs when the staple legs are not driven straight through and into the holes in the bottom plate and are deflected or bent by the engagement with the bottom plate rather then passing through the holes in the bottom plate. Although the guide blocks provide a general guide of the power driven tool, there still can exist a particular inclination or lean of the gun, particularly a lean in one leaning direction versus another leaning direction, that may cause a misfire. For a commercially successful system, the number of misfires must be minimal.
From the foregoing it will be seen that the prior commercial belt fastening systems have a number of shortcomings and problems, not all of which are discussed above. Also, it will be seen that there is a need for a faster belt fastener attaching system to address the shortcomings and problems of the prior systems.